Correcting soil pH problems is one of the first steps in good soil management.

If you have soil sampled recently and found that pH is low, you should act on it. Soil pH affects the availability of a wide range of nutrients in soil; if it is too low or too high, nutrients are less available to crops. If pH drops too low, e.g. below 5, aluminum toxicity can become an issue. Acid soils can also negatively impact nodulation of forage legumes, persistence of perennial forages and growth of sensitive plants, such as wheat.

There are two values to key in on when reading a soil test:

Soil pH tells you if lime is needed. Typically, if you have wheat or field vegetables in rotation, lime is beneficial when soil pH is below 6.1 on medium or lighter textured soil. For clays and clay loams, it’s needed when pH is below 5.6 (see Table 9-4 in Publication 811).

Buffer pH tells you how much lime is needed. The lower the buffer pH value, the more lime will be required to raise the pH to a desired level. For example, soil with a buffer pH of 6 requires two to three times the lime of a soil with a buffer pH of 6.5 (Table 1). Clay and organic matter provide what’s called “reserve acidity,” which is a supply of hydrogen ions held by soil particles. This is why heavier textured soils tend to have a lower buffer pH and require more lime to increase soil pH.

1 Buffer pH in Ontario is measured using the Shoemaker, MacLean and Pratt (SMP) buffer. Other jurisdictions may use different buffers, which will give similar but not identical results.

2 Lime if soil pH is below 6.1

3 Lime if soil pH is below 5.6

4 Lime if soil pH is below 5.1

Once you have determined your target pH and the lime requirement, it’s time to compare products.

Limestone quality is determined by how well the lime can neutralize acidity and how finely it’s ground. These values are combined into what’s called the Agricultural Index. OMAFRA lime guidelines are based on an Ag Index of 75. It’s essential to compare prices of lime based on relative Ag Index values. For example, a product that costs $20 per ton with an Ag Index of 95 is a better deal than a product that costs $15 per ton with an Ag Index of 65 (see below).

The choice between calcitic and dolomitic lime is simple: if your soil test level for magnesium is below 100 parts per million, use dolomitic lime; if it is higher, use either type.

If you work with a lab or ag retailer to have grid or zone soil sampling done on your fields, the same principles apply for soil pH and liming, just at a finer scale. Prescriptions are based on soil variability and can allow for a more accurate (and potentially cost-effective) lime application across the field.

The bottom line: Soil sample regularly to monitor soil pH if you know it can be an issue in your area. If your soil test calls for lime application, follow the guidelines above to make an accurate and cost-effective decision on rate and product. Addressing soil pH is an essential component of managing soil fertility.

Before long, the 2018 winter wheat crop will be seeded across the province (Figure 1). Long-term research at the University of Guelph’s Ridgetown campus shows that winter wheat in rotation provides an additional 10 bushels per acre to corn and 5 bushels to soybeans. At current crop prices, that means an extra 107 dollars per acre over a rotation.

Figure 1. Winter wheat field in Perth County, April 2017

What other benefits does wheat provide? And how might having wheat in rotation be positive from a soil fertility perspective?

Firstly, wheat in rotation improves the nitrogen use efficiency of corn. Recent research from the long-term rotation and tillage system trial in Ridgetown demonstrates that winter wheat in rotation reduces the maximum economic rate of nitrogen, or MERN, for corn. Between 2009 and 2013, the average MERN was 16 to 30 lbs/ac less with wheat compared to a corn-soybean rotation; in other words, it took less nitrogen to produce more corn.

Wheat also provides an opportunity to seed a cover crop. In the case of red clover (Figure 2), the economics are clear: a full stand of red clover provides a nitrogen credit of 65-80 lbs per acre to the following corn crop. If red clover establishment is difficult, another cover crop, such as oats, can be seeded. Although oats will not provide any nitrogen, its fibrous root system will set up the next crop with improved soil structure – this is particularly helpful in dry years, where a good root system is critical for nutrient uptake.

Figure 2. Red clover cover crop

Winter wheat in rotation is also beneficial from a soil organic matter standpoint. Ontario research has generally found that the more frequently a small grain like wheat is in rotation, the higher the soil organic matter. Roots and belowground residue tend to contribute more to stable organic matter than aboveground residue, which may explain the positive effect of deep-rooted wheat. Organic matter is an important source of nutrients such as nitrogen, sulphur, phosphorus and boron.

Finally, having winter wheat in rotation provides an excellent opportunity to address soil test levels. Use the period after wheat harvest to take soil samples. If you have soil test levels that have slipped in the last number of years, post-wheat harvest is an excellent time to make a nutrient application.

A recent review of decades’ worth of Ontario research has shown that when soil test phosphorus is within the range of 12-18 ppm (Olsen), starter fertilizer rates (i.e. 20-30 lbs P2O5/acre) achieve the most economic response for field crops. The same is true for potassium when levels are between 100-130 ppm. More recent research from OMAFRA/University of Guelph long term P and K trials suggest that slightly higher soil test values (e.g. >20 ppm P and >120 ppm K) may be worth pursuing in some circumstances.

Regardless of your field’s soil fertility status or your fertility plan, broadcast fertilizer applications made in the summer after wheat harvest are at much lower risk for environmental losses relative to applications made in the late fall.

There you have it – a few more reasons to keep wheat as a regular part of your crop rotation.

It is National Soil Conservation Week this week, so I thought it would be a good opportunity to look at the impact of erosion on soils in Ontario over the past few months.

Throughout the middle of April we’ve had some intense rain events. We had a mild winter this year in southwestern Ontario, with little snow cover, and had some very windy days. In some cases, water carried soil away (Figures 1 & 2). In other cases, wind whipped it up and carried soil off of fields (Figure 3).

Very soon the 2017 growing season will begin and these soil losses will be forgotten. But what was the impact of the soil that moved? What is the cost of the lost soil and fertility?

Figure 1. A long slope on a field near Port Colborne, Ontario in late January. With minimal residue cover, water picked up momentum and eroded soil along the entire length.

Figure 2. Gully erosion on heavy clay soil in Haldimand county, April 2017. How much soil has been carried away?

Figure 3. Wind-blown topsoil on snow in Perth county, March 2017. Was this soil lost from a bare field or one with residue or plant cover?

During a very windy day in early March, topsoil in Kent county was blown into ditches to a depth of 1 to 3 feet in some locations (Figure 4).

Figure 4. What fertility has been lost from the field due to this wind erosion? Kent county, March 8, 2017. Photo: Colin Little, Lower Thames Valley Conservation Authority.

A sample of the wind-blown soil in a ditch was taken and sent away for fertility analysis. The numbers are presented below:

Nutrient

Value

Organic Matter*

9.4%

Phosphorus (Sodium bicarbonate/Olsen)

37 ppm

Potassium

282 ppm

Magnesium

683 ppm

*Measured using the Walkley-Black method.

In a part of the province where average soil organic matter levels are around 3.5%, this wind-blown soil was clearly coming from the most fertile portion of the soil – the soil surface.

To borrow from Peter Johnson’s “Wheat Pete’s Word”, if we assume a land value of $20,000 per acre, each pound of topsoil is worth 1 cent (based on 2 million pounds of soil in the top six inches). If the thickness of a couple pieces of paper is lost from a field, it represents one tonne per acre, or $22, of soil loss. Of course, when the most fertile topsoil is lost, the value is even greater. Given the impact of organic matter, phosphorus and potassium on yield potential, soil erosion can be costly.

Fortunately, there are well proven solutions to minimize soil erosion. Here are examples of a few.

Figure 5. Overwintering cover crops, such as cereal rye, can be very effective in holding soil in place, even under very intense rain. This rye, planted after sweet corn, has held soil on an erodible slope. Photo: Michael Funk, Upper Thames Region Conservation Authority. March, 2017.

Figure 6. Cereal rye cover crop in Brant county, mid-April, 2017. Seeded after corn silage harvest to protect soil from water erosion that is typical on this field. It has done its job.

Figure 8. Grassed waterways can also be an effective method for minimizing water erosion in some fields. (Source: Jane Thomas, Integration and Application Network, University of Maryland Center for Environmental Science, ian.umces.edu/imagelibrary/).

When soil is unprotected it can easily be lost, as we’ve seen this winter and spring. And all losses have a soil fertility impact – in some cases, it is greater than we might think.

Crop yields have increased significantly since fertility recommendations were developed in Ontario. Crop nutrient uptake and grain nutrient removal have increased proportionately. A study was initiated in 2011 with funding from the Grain Farmers of Ontario to evaluate a corn-soybean-wheat rotation on four sites with relatively low soil test P and K levels. Areas within each test site were built to moderate P, moderate K, and moderate P and K soil test levels (P>20 ppm, K>120 ppm). High rates of P and/or K fertilizer were applied during the first few years of the study to build these areas. These built P and K soils can now be compared to soils with low background fertility. This project will test if current P and K recommendations ensure the most economic yields in high yield environments. Ontario recommendations are based on the “sufficiency approach” which aims to supply enough fertilizer for a given crop with the most economic rate of fertilizer for the year of application. Another approach to fertilizer application is the “build and maintain” approach which aims to build or draw down soil tests to a reasonable level and maintain soil tests at those levels. These two approaches to fertilization will also be compared.

Methods

Fertilizer was broadcast at high rates across specific blocks in every year to build up fertility (400 lbs/ac of product). One block was built with only P, another only K, and a third had both P and K built. An untreated block with low background fertility was left untreated at each site. All blocks and starter treatments were replicated 4 times whenever possible. The highest starter treatment rates were 50 lbs/ac of actual P and 50 lbs/ac of actual K. These starter rates were chosen to supply the approximate rates of recommended fertilizer under the “sufficiency approach”. Soil test values have now been built to moderate levels in those blocks that received fertilizer to the desired levels (P>20, K>120). Yield data from the next three growing seasons (2017, 2018, and 2019) will give the best comparison of the “sufficiency” approach to the “build and maintain” approach since previous years may have been influenced by the build-up phase of the experiment. Tables 1 to 3 present the most up to date yield results based on the last 3 growing seasons.

Results

Corn yields responded to a starter blend of P and K in low background fertility levels (P<20, K<120) by 30 bu/ac across the 17 site-years of this study. On “built” soils (P>20, K>120) corn responded to a P and K starter by 10 bu/ac (Table 1). The highest corn yields were achieved with a built soil test value plus a starter fertilizer containing P or a starter containing a blend of P and K. Averaged across background fertility, liquid starter added 9 bu/ac, dry P added 12 bu/ac, K added 13 bu/ac, and the P and K together added 22 bu/ac compared to no starter fertilizer. This study supports earlier findings that corn is highly responsive to starter fertilizers especially when soil test levels are low. It also demonstrates that even when soils are built starter fertilizers are still necessary to maximize yields. Most notably corn yields were 13 bu/ac higher on built soils compared to low background fertility even when a high rate of P and K starter was applied.

Means followed by the same letter are not statistically different within a column at P=0.05.

Soybean yields responded to a starter blend of P and K in low background fertility soils (P<20, K<120) by 4 bu/ac across the 17 site-years of this study. On “built” soils (P>20, K>120) soybeans did not respond to any starter fertilizer treatment. The highest soybean yields were achieved with a built soil test value. Averaged across background fertility, liquid starter added 1 bu/ac, dry P added 2 bu/ac, K added 1 bu/ac, and the P and K together added 3 bu/ac compared to no starter fertilizer. On low background fertility soils, liquid starter added 2 bu/ac, dry P added 2 bu/ac, K added 1 bu/ac, and a blend of P and K added 4 bu/ac compared to no starter fertilizer (Table 2). This study supports earlier findings that soybeans respond to starter fertilizers when soil test levels are low. This study has shown that K by itself is not sufficient to maximize soybean yields, P is also critical. This study also supports earlier findings that when soils are built starter fertilizers do not add yield to soybeans. Soybean yields were 4 bu/ac higher on built soils compared to low background fertility even when a high rate of P and K starter was applied.

Means followed by the same letter are not statistically different within a column at P=0.05.

Figure 1. Severe K deficiency (left) in soybeans.

Winter wheat yields responded to a starter blend of P and K in low background fertility levels (P<20, K<120) by 14 bu/ac across the 13 site-years of this study. Wheat showed the same response to a P only starter on low background fertility soils (14 bu/ac). On “built” soils (P>20, K>120) wheat did not show a statistical yield response to any starter fertilizer over the untreated although the P only starter did provide a 4 bu/ac numerical advantage over the untreated (Table 3). Averaged across background fertility, liquid starter added 4 bu/ac, dry P added 10 bu/ac, K provided no additional yield, and a blend of P and K together added 10 bu/ac compared to no starter fertilizer. This study found that wheat is responsive to starter fertilizers especially when soil test levels are low. It also demonstrates that winter wheat is highly responsive to starter P. Most notably wheat yields were 11 bu/ac higher on built soils compared to low background fertility even when a high rate of P and K starter was applied.

Means followed by the same letter are not statistically different within a column at P=0.05

Figure 2. Wheat on the left had phosphorous (11-52-0) applied and on the right had potassium (0-0-60) applied, demonstrating the importance of P in wheat production.

Conclusion and Next Steps

On most crops and field site locations, starter fertilizers increased yields compared to no fertilizer, especially in wheat and corn and on soybeans when soil P and K levels were low. The highest yields tended to be produced from plots with moderate background P and K (broadcast P and K) in conjunction with a starter. Soybeans did not show a response to starter fertilizer on soils with higher background fertility. Now that specific plots have been built to moderate levels of P and K, and other plots have relatively low soil test P and K levels, fertilizer management strategies may be tested (the “sufficiency” versus the “build and maintain” approach). Yields to date show that building the soil adds 13 bu/ac of corn, 4 bu/ac of soybeans, and 11 bu/ac of wheat compared to fertilizing the crop under the present rates of the sufficiency approach. It is crucial that this experiment be continued for at least 3 additional years to get the most robust comparison of the two systems. An economic analysis will be conducted at the end of this study to determine which approach is the most economical way to grow crops in Ontario.

Sulphur (S) deficiency was very prevalent in winter wheat last spring, including fields with a history of manure applications (Photo 1). The deficiency seen in many fields may have resulted from a cooler than normal April reducing S mineralization.

S applications may not be required every year due to the year to year variation in response which might have you asking the question, why bother with S applications? Well, historically S deficiency in winter wheat was not an issue; however, since sulphur oxide emissions have decreased significantly, there is a need to ensure the crop has an adequate supply of S.

Ontario research has shown there is a variation in yield responses to S applications depending on the year. Years with cool, damp spring conditions showed more of a yield response (Table 1). Interestingly, when the data was analyzed further and separated into responsive and non-responsive sites, yield gains were even more significant on responsive fields (Table 2).

So, as we start thinking about fertility management this spring, don’t forget about sulphur. Pay close attention to the temperature and if the weather continues cool into the spring as wheat advances an application of S may be needed. Get out and walk your fields and if you are seeing deficiency symptoms (Photo 2) consider a tissue analysis to confirm. Ontario research suggests yield responses for S applications when tissue-S concentrations are below 0.25, while tissue-S concentrations above 0.30 rarely show a response.

Photo 2: Sulphur deficiency can be identified as whole plants that are pale yellow. It can often be found first on slopes and areas with low organic matter.

Although a tissue test will assist in determining whether you have S deficiency, it may not be as helpful in determining the optimal rate to apply. Ontario research suggests that the optimal rate is 10 lbs/ac. However, some fields may require a higher rate so do some test strips in your fields to compare yields and identify responsive and unresponsive fields. If you are seeing a deficiency, apply S as soon as possible. Once an application of S has been made a response is typically seen in 3-4 days, but as we saw this past season it can take up to 10-14 days.

Cover crops are well proven to help reduce soil erosion and improve soil structure. They can also have nutrient benefits. Whether you have been growing cover crops for decades or are just getting started, it is helpful to know what specific cover crops can (and cannot) do from a soil fertility standpoint.

There are three main ways that cover crops can provide a nutrient benefit within your cropping system:

By fixing atmospheric nitrogen and providing a plant-available nitrogen to the following crop

By preventing nutrient losses that would otherwise occur (through leaching or surface runoff)

By improving soil nutrient cycling

Some species of legume cover crops can fix hundreds of pounds of nitrogen per acre. The important value, however, is how much of that nitrogen becomes available for uptake by the following crop. A full, uniform stand of red clover (Figure 1) provides a nitrogen credit to corn of approximately 60-70 lbs/acre, for example. There have not been specific nitrogen credits established for other legume cover crops in Ontario.

Figure 1. Stand of red clover in early fall following wheat harvest.

Growing a deep-rooted cover crop reduces the amount of nitrate nitrogen that can be lost to leaching over the fall, winter and spring. If you want to retain nitrogen over winter, seeding a grass or cereal, such as cereal rye, can be very effective. Plants with deep taproots, such as radish, can also capture nitrogen from depth, though in some cases the timing of nutrient release may occur early in the spring, before uptake by a crop such as corn. The most effective cover crops for reducing nitrate loss are those that gain a reasonable amount of biomass in the fall and/or spring and have both dense and deep root systems.

By providing cover on the soil surface, cover crops can also reduce nutrient losses from soil due to surface runoff. Over the long term, cover crops will improve soil structure, which will increase water infiltration and water holding capacity and likely reduce the risk of soil erosion.

When they freeze, however, cover crops can release dissolved phosphorus. The amount released depends on the species. Some of the dissolved phosphorus may go into the soil during thaw events, while some may be lost to surface runoff from the field. Research is underway in Ontario to determine which species and termination methods result in the lowest risk of phosphorus losses to surface water.

Overall, the value of certain cover crops in reducing erosion, improving water infiltration, and reducing nitrate leaching makes them a good option for preventing nutrient losses from your fields.

Cover crops can also improve nutrient cycling. What does this mean? It means that cover crops, through the sugars they release from their roots and their residue, provide food for soil life. By stimulating soil biological activity, cover crops can accelerate crop residue decomposition and cycling of nutrients from organic (unavailable) forms to inorganic, plant-available forms. For example, cover crops are consistently found to improve earthworm populations (Figure 2), which play a very important role in nutrient cycling.

Figure 2. Earthworm casts in a field with cover crops. Earthworms play an important role in nutrient cycling in soil.

Certain cover crops can also provide deep nutrient recovery. Deep-rooted cover crops, such as forage (tillage) radish (Figure 3), cereal rye or turnip, bring a variety of nutrients from depth to the soil surface, where they can be more easily taken up by the following crop. Such cover crops grow in the fall and possibly spring, when moist soil conditions allow for easier root penetration, even in heavy soils. This provides the additional benefit of deep root pathways that can be used by cash crop roots in the next season.

Figure 3. The taproot of forage (tillage) radish can extend deep into the subsoil

Cover crops are not a magic bullet for soil fertility, but they can be an effective tool when managed properly. While some benefits are short term, such as a nitrogen credit from a legume, others will begin to show up over a longer period of time. Success often depends on matching up the right cover crop species with good management and specific goals. If you are new to cover crops, it is best to start small and gain confidence. For more information, visit the Midwest Cover Crop Council’s website or the OMAFRA Cover Crops website.

We live in interesting times when it comes to understanding soils. Our concept of what soil organic matter actually is, how it is formed, and how long it sticks around is evolving. The basic principle that has guided management of soil organic matter (SOM) for many years has been that the level of soil carbon is determined by its net input. In other words, high yields mean high residue return, which results in a build-up over time of SOM. Makes sense, right? Mostly, but it turns out that there’s a bit more to it. In this article, I will highlight some of the latest understanding of soil organic matter and discuss which management strategies can be used to restore and maintain it in your soils.

At FarmSmart 2016, Dr. Jerry Hatfield of the USDA spoke about the importance of soil organic matter. He highlighted the need to improve soil water holding capacity to reduce the impact of climate variation that is anticipated across the US Midwest and Ontario in the coming years. Dr. Hatfield’s key message was to build soil organic matter to ensure abundant and stable production in the face of less predictable summer rainfall.

Soybeans in a field with a history of reduced tillage, cover crops, and manure application (2016 season; Brant county)

Soil organic matter performs many different functions and is an incredibly important component of soil. We know that it stores and supplies nutrients, improves soil structure and water infiltration, supports soil biological activity, and buffers against changes in soil pH. Higher soil organic matter levels translate into better water holding capacity, which is critical in a season like the one we are having so far. We also know that it can, and is, regularly lost – either through oxidation or erosion.

And as farmer Ken Nixon said of organic matter at last March’s Soil Health Roadshow, “you can’t buy it; you have to earn it.”

But how much do we really know about soil organic matter and how it is “earned”? What role does crop rotation play? What about organic amendments? Finally, how can cover crops help build soil organic matter?

Here are a few key concepts that will help answer these questions:

Soil organic carbon vs. soil organic matter (SOM)

You may hear the terms soil organic carbon and soil organic matter used interchangeably. The two are related, but aren’t the same. Here’s the difference:

Organic carbon is the carbon component of soil organic matter (SOM). On average, SOM contains 58% carbon, which means that you can roughly convert organic carbon to SOM using a factor of 1.72.

SOM is made up mostly of carbon, but also contains hydrogen and oxygen, and nutrients such as nitrogen, phosphorus, sulphur, potassium, and many more.

Carbon is added to the soil by the process of photosynthesis: carbon dioxide is “fixed” by plants (and certain microbes). The fixed carbon makes it way to the soil through crop residues as well as root exudation.

First, soil microbes are now believed to greatly influence SOM cycling in the soil not only because they decompose residue, but also since microbes themselves (once they die) and their by-products can be significant components of organic matter in soil.

Second, residue and amendment quality (i.e. carbon-to-nitrogen (C: N) ratio) has been found to play an important role in the accumulation of soil carbon. Recent research shows that without a balance of residue types, you may not be building SOM as quickly as you think.

Third, the latest science shows that carbon from root material is retained in soil more efficiently than aboveground inputs. This new knowledge may fundamentally change how we think about building soil organic matter.

The role of soil microbes in soil organic matter

We have long known that soil microbes and larger soil organisms play an important role in cycling organic matter in soil. Microbes decompose plant residue and, in doing so, release carbon as carbon dioxide (CO2). They also use a portion of the carbon for their bodies, which are themselves part of the “soil organic matter pool.” It has recently been found, however, that soil microbes also influence SOM cycling because dead and dormant microbial cells and by-products are a significant component of soil organic matter itself.

Given that soil microbes themselves are such important contributors to soil organic matter, but also play an important role in decomposition, how do you manage your soil so that you’re balancing the two?

Dr. Lisa Tiemann, a soil microbial ecologist from Michigan State University and 2016 Southwest Agricultural Conference (SWAC) presenter, described the situation as the “soil organic matter conundrum.” At her SWAC presentation, the question she posed was: how do we simultaneously support microbial growth and nitrogen mineralization and maintain and build soil organic matter?

At the heart of the explanation, Dr. Tiemann argued in her talk, is nitrogen. On average, soil microbes contain 8 parts of carbon for every 1 part of nitrogen (their C: N ratio). As microbes consume plant residue, around two thirds of the carbon is lost as CO2 and one third is taken into their biomass. This makes the C: N ratio of 24:1 critical (since one third of 24 is 8). Residues below 24:1 are broken down quickly and stimulate microbial growth since they provide easily available nitrogen. On the other hand, residues above 24:1 contain more carbon relative to nitrogen than the microbes require. This means that existing microbial populations need to find nitrogen from other sources, such as existing SOM.

Two main groups of microbes are important when it comes to soil organic matter. Fast-growing microbes reproduce rapidly, thrive on low C: N residue (think young alfalfa), and are generally inefficient (gain a relatively small amount of energy per amount of carbon consumed). Slow-growing microbes, on the other hand, reproduce slowly, feed on high C: N residue (think wheat straw and corn stover), but are energy efficient.

Dr. Tiemann stated that the best way to build and maintain organic matter is to strike a healthy balance between the two types of microbes. She offered the following advice for doing so:

1) Wake up soil microbes

By growing cover crops to feed and build soil microbial populations during the fall and early spring

By applying organic amendments if possible, which have been shown to have a dramatic effect on stimulating microbial growth

2) Provide a mixed quality of amendments over a rotation

High quality (low C: N) amendments, such as legume and immature grass cover crops, help stimulate fast-growing microbes and provide short-term N release. Low quality amendments, such as mature grasses and manure with plenty of bedding, feed the more efficient microbes, such as fungi, that help build stable, long-term SOM.

3) Diversify your crop rotation – more diverse rotations in general have higher SOM and more active and diverse microbes

Ontario research shows that adding winter wheat to a corn-soybean rotation improves soil carbon levels over time. When red clover is included as a cover crop, it likely contributes to soil organic matter not only due to its biomass, but also because it provides a high nitrogen residue that balances the high carbon residue of wheat and corn. Better yet, by leaving red clover growing throughout October (or later), you will get double the root growth, as Dr. Dave Hooker has shown, which further enhances the benefit.

Legumes, like this stand of red clover, play an important role in stabilizing soil organic matter by adding high N content residue

Roots vs. shoots

Often the success of a cover crop is judged by its aboveground growth. However, new data suggest that what’s going on belowground may be even more important if it is soil organic matter you’re after. Research has consistently found that carbon from roots is more stable in soil than aboveground residues. In other words, carbon from roots sticks around in soil longer than carbon from shoots. This is likely because inputs from roots have better opportunities to interact with soil than aboveground residue, like leaves and stems. So, if you’re looking to build soil organic matter, achieving a consistently good root system matters.

What does this mean?

Better soil structure and better crop root growth translates into higher yields, and also contributes more to long-term organic matter as those roots break down

Maximize root growth with cover crops. Don’t judge a cover crop entirely by its aboveground looks – do a little digging to check root growth, and give credit for what you see belowground. Species such as oats and cereal rye are known to have excellent fibrous root systems.

Root system of a cereal rye cover crop.

Principles for building and maintaining soil organic matter

When it comes to building soil organic matter, one positive action can often have multiple benefits. Here are some principles to keep in mind for enhancing organic matter in your soils:

If you don’t grow wheat and you can, start (or better yet, a perennial forage)

Apply organic amendments for their carbon and nutrient value and to “wake up” soil microbes

Focus on shoots and roots

The bottom line

Soil organic matter is the single most important soil property that you have influence over through your management. Higher soil organic matter levels translate into higher yields, more consistent yields, and higher profit in the long run. What’s keeping you from getting started?

Regular soil testing is a critical component of good crop production. It allows you to monitor soil fertility levels, identify potential for nutrient deficiencies, and make fertilizer decisions based on the best possible information. Perhaps you had samples taken this fall and sent off, and have received the soil test report back (see Figure 1 for an example). Whether you opted for grid sampling, zone sampling, or just a regular composite sample, it can sometimes be a challenge to understand exactly what those numbers mean and how to use them to make decisions. Also, if you’ve been given a fertilizer recommendation, it is useful to be able to double check to make sure it’s in the right range.

When a soil sample is submitted to the lab, it is dried and ground and a variety of extractions are performed on small “sub-samples”. It’s important to bear in mind that these sub-samples may be as little as 2 grams of soil, so it is critical to obtain as representative a sample as possible. The extractants pull the easily and some of the moderately available nutrient from the soil. The soil test value for a given nutrient does not give you the total amount of that nutrient in the soil; it instead provides an index of nutrient availability that is correlated with plant response. For the base cations (potassium, calcium, magnesium), the value represents the “exchangeable” form of the nutrient – the portion that is attached to clays and organic matter and available to move into soil solution.

Soil test values are reported in parts per million (ppm), which represents 1 milligram of extracted nutrient for each kilogram of soil. If you want to estimate the value in pounds per acre, you can simply multiply the ppm value by two to obtain pounds per acre. For example, a potassium soil test value of 193 ppm equates to 386 lbs/acre (of “exchangeable K” in the top six inches of soil).

Pay attention to the extractant used for your soil test. For example, the Olsen (or sodium bicarbonate) extraction is the OMAFRA-accredited test for phosphorus. OMAFRA fertilizer guidelines are based on the Olsen test. Be sure that you are not accidently confusing a Bray-1 P soil test result with an Olsen result. Depending on the lab you use, each OMAFRA-accredited test value should also have a code associated with it. The code will give you a sense of how likely you are to have a profitable response to an application of that particular nutrient (e.g. LR means that there is a low likelihood of response to that nutrient, since the background level is relatively high).

In terms of which values to focus on, soil pH should always be a starting point. Refer to pg. 158 of Publication 811 to determine when lime is recommended. Percent organic matter is another critical measurement – monitoring its value over time can tell you quite a bit about how well your soil management practices are working to maintain or build it. Macronutrients, in particular phosphorus and potassium, should be the next area of focus.

Fertility guidelines

OMAFRA fertilizer guidelines, which can be found in Publication 811, are based on the sufficiency approach, which provides the greatest potential economic response in a given year based on crop and soil test level. Depending on your situation, you may want to invest in raising soil test levels for phosphorus or potassium. A recent review of decades’ worth of Ontario research showed that when phosphorus is within the range of 12-18 ppm (Olsen), starter fertilizer rates (i.e. 20-30 lbs P2O5/acre) achieved the most economic response for phosphorus. The same was true for potassium when levels were between 100-130 ppm.

It is generally assumed that the following amounts are required (above crop removal) to move soil test values up by 1 ppm:

35 lbs/acre P2O5 and 20 lbs/acre K2O

These values are guidelines and can vary depending on a variety of factors, including soil type. In some situations, the amount of nutrient required to raise soil test values may be lower. If you had a field sitting at 10 ppm P and 80 ppm K, P and K above crop removal could be applied over a number of years to reach targets of 15 ppm soil test P and 115 ppm exchangeable K. Variable rate technology is available to apply these nutrients according to where they are needed on the field.

It is important to bear in mind that nutrients behave differently in soil. Because of how reactive phosphorus is in the soil, as much P as possible should be banded to provide optimal benefit to the crop in the growing year. If phosphorus is broadcasted, it should be done so during a time period when risk of soil and nutrient loss due to runoff is low (e.g. late summer after wheat harvest).

Consider alternative nutrient sources as well if they are available in your area. Sources such as municipal compost, processed biosolids products, and manure (if available), can be used to address fertility levels and have the added benefit of contributing to soil organic matter and improving soil structure over the long-term.

Soil organic matter (OM) is the single most important soil health property that you have influence over through your management. Soil OM is all living, dead or long dead (and decomposed) material. Higher soil organic matter translates into better water holding capacity, which was critical in a season like 2016. It helps to improve soil structure and nutrient cycling. A higher percent organic matter can also mean more consistent yields year-to-year. Simply put, it is the foundation of a healthy soil.

Dark coloured topsoil indicates good levels of soil organic matter

Often, it is stated that nitrogen (N) fertilizer application helps to build soil organic matter by increasing total crop production. The logic follows that a higher yielding crop returns a greater amount of residue, which can then break down and contribute to soil OM. There have been a variety of scientific studies that have shown this to be true. However, nitrogen fertilization can also stimulate organic matter mineralization, which can lead to losses of OM and soil nitrogen. There is also research that shows no effect of N fertilization on soil organic matter over time.

Overall, it is safe to say that research findings on the effects of N fertilization on OM have been inconsistent in annual crop production systems. Because OM changes can only be detected over the long-term, it is difficult to determine the effect of N fertilization in different production systems with climates similar to Ontario’s. For example, what is the impact of crop rotation? What role does tillage play? And how are deeper soil layers affected by nitrogen fertilization? A recent study conducted at the Ridgetown Campus of University of Guelph by Drs. Katelyn Congreves, Laura Van Eerd and Dave Hooker used the long-term crop rotation and tillage system trial to answer these questions.

The study

The research compared N rates across continuous corn, corn-soybean, and corn-soybean-winter wheat crop rotations under no-till and conventional tillage. Conventional tillage consisted of moldboard plowing in the fall followed by two to three passes with a field cultivator in the spring for corn and soybeans. Prior to wheat planting, two passes were made with either a tandem disc or cultivator. In the no-till treatment, there was zero tillage and only minimal soil disturbance at planting. As for N rates, starter-only rates were compared to starter plus moderate N fertilization to corn (89 lbs/ac N) and wheat (71 lbs/ac N) amongst crop rotation and tillage treatments. Samples were collected in 2006, 11 years after the establishment of treatments.

University of Guelph’s long-term crop rotation and tillage system trial in Ridgetown

What did they find?

So, after 11 years did nitrogen fertilization help increase soil organic matter at the Ridgetown site?

Well, it depended. The greatest increase in OM due to N fertilization occurred in the corn-soybean-winter wheat rotation in both tillage systems. Soil OM was increased by 18 to 28% in the top 8 inches in the plots that received nitrogen fertilizer. Under continuous corn, however, N fertilization did not change soil organic matter levels in either tillage system. In the corn-soybean rotation, N fertilization increased OM by 22% in the no-till system only; no change was observed with plowing. Even down to a depth of 3 feet, the corn-soybean-winter wheat rotation showed the greatest increases in OM in response to N fertilization. Belowground biomass from a deep, fibrous-rooted wheat crop and growth during a typical fallow period may have contributed organic matter that is retained in the soil more easily compared to other crops.

Even more interestingly, corn yields from years 5-11 of the study revealed the benefit of an increase in OM. Year-to-year yield variability decreased as soil organic matter level increased. This meant more consistent corn yields regardless of the weather. Likely, this was due to soil OM benefits in terms of increased water infiltration and improved water holding capacity.

The bottom line

Nitrogen fertilization does not necessarily increase soil organic matter across all agricultural systems. Its effect depends on crop rotation and tillage system. For the clay loam soils of this study, there is clear evidence that inclusion of winter wheat in a corn-soybean rotation makes an increase in soil OM due to N fertilization more likely, regardless of tillage system.

We know that winter wheat in rotation benefits corn and soybean yields by 5 to 8%, reduces year-to-year yield variability in corn, improves soil health, and provides an excellent cover crop opportunity. Its value goes far beyond its net revenue at harvest. Now, this research suggests that wheat may also help make better use of N fertilizer from a soil organic matter perspective. Just another reason to add to the list.

Next steps

In 2008, Dr. Hooker made improvements to the trial to better reflect current production systems. The no-till treatment was modified to strip tillage for corn and nitrogen rates were increased in both corn and wheat. Winter wheat plots were split to include both with and without red clover treatments. These changes provide an excellent opportunity to study the effects of these production systems on soil health into the future.

Wouldn’t it be nice if liquid manure application could wait until after corn planting was completed, with little risk of compaction or damage to corn plants?

It may be the dog-days of summer, but kicking tires at an equipment demonstration and field day is a good way to evaluate how the newest technology may fit into your operation at some point in the future. The North American Manure Expo, held August 3-4th, 2016 near London Ohio, provided an opportunity to watch a variety of new manure application equipment. Each year, Ontario manure equipment manufacturers demonstrate that they are industry leaders in manure application innovation.

In particular, the liquid manure demonstrations at this year’s Expo focused on in-crop application opportunities. The benefits of in-crop application are that they can:

increase the economic benefit of the nutrients in manure by placing them where the crop can use them when the crop needs them.

reduce compaction by applying nutrients when the soil conditions are fit

reduce phosphorus movement to water courses, compared to applications during the non-growing season

benefit the soil microorganisms by increasing the biomass, and organic matter returned to the soil

Introduced for the first time this year was the Cadman Power Equipment Continuous Manure Applicator (CMA), an in-crop drag hose system. The (CMA) was engineered to apply liquid manure via side-dress to row crops (30 inch row spacings) in fields as long as 2500 ft. (800 m).

The tractor pulls the injector with a patented swivel arm and 5.1 inch hard hose away from the CMA reel, as shown in Figure 1 and 2. When the tractor gets to the opposite end of the field, it turns 180o to the next set of rows and comes back down the field (Figure 3). When the tractor turns, the swing arm moves to the side of the tool bar, therefore keeping the hose in the same row that it was pulled out on. The tractor returns at the same speed it was pulled out at to synchronize with the reel rewind speed. When the tractor returns to the starting point, the 4 wheel drive CMA reel and steering is controlled remotely from the applicator tractor cab. While the operator is completing the return trip, the remote automatically moves the CMA reel and hard hose forward 60 or 80 ft to start another pass.

Figure 2: Cadman Continuous Manure Applicator (CMA) reel unrolling the hard hose as the tractor and injector move to the opposite end of the field.

Figure 3: The tractor and toolbar have moved to the next set of rows while the swing arm moved to the side to allow the hard hose to rewind onto the CMA reel.

The toolbar can be fitted with injection units including Aerway®, Dietrich, Yetter, or other options such as the dribble bars (figure 4) that can manure match application into a variety of growing crops and row spacings at various opportunities during the growing season.

Figure 4: Toolbar options that include dribble bars or shallow injection tools to apply into standing corn up to side-dress timing. Specialty tool bars are being designed to allow cover crop seeding to occur with manure application.

Other innovative equipment demonstrated at this year’s manure expo included:

Solid manure application with high or close to ground application to help match solid manure (material) type, application spread width, and wind speed to improve uniformity and accuracy of application.

The Nuhn Lagoon Crawler, (figure 7) which is an amphibious pump designed for agitating large lagoons. The pump can drive itself into the lagoon, mix the lagoon as a boat, and then drive itself out when the pit is empty

Co-Authored with Ian McDonald, OMAFRA and Ken Janovicek, University of Guelph

OMAFRA Field Crop Unit staff have traditionally conducted a Pre Sidedress Nitrogen Test (PSNT) survey across Ontario at the beginning of June each year to examine the natural soil nitrate available. In the past, 80-100 samples would be collected from fields across the province that had not received any preplant nitrogen other than up to 30 lbs of N banded at planting.

In 2016, we are transitioning to reporting the results of the GFO supported Soil Nitrogen Sentinel project (http://bit.ly/1WMzSb4). The goal of the project is to collect samples over time from several permanent sentinel locations to better understand how natural soil nitrate levels change over the spring. Soil organic N mineralizes over time in the spring at different rates due to temperature, moisture, soil texture, crop rotation among other factors.

Soil samples were collected from 23 locations beginning at planting time (~May 1), through the V1-V2, V3-V4, crop stages with additional sampling events planned for the V6 and V9 stages where “V” designates visible collars on the corn plant. The V3-V4 sample timing coincides with the historical annual PSNT survey, and together with data from an additional 12 supplementary sites is included in this years survey. Ongoing results for the Nitrogen Sentinel project are available at http://bit.ly/1rd6z3F.

In general, the spring of 2016 has been cooler and drier than average through April and May, although accumulated CHU’s have caught up to above normal as of the last week of May. While cooler and drier conditions may reduce nitrogen mineralization from organic sources (supply) in the soil, the drier conditions reduce the potential for loss through leaching or denitrification.

A total of 35 samples were collected from June 6 to June 7 in corn generally in the V3-V4 stage from locations scattered throughout Southern Ontario, as well as a few in central and eastern Ontario. With an overall average of 11.2 ppm in 2016, soil nitrate levels tended to be average or slightly above average relative to the 5 previous survey years (2011-2015), while slightly lower than 2015 values which were well above normal (Figure 1).

Figure 1. PSNT survey results by soil texture for years 2011-2016.

PSNT values were similar on fine and medium textured soils (Table 1), but lower on coarse textured soils, which is generally consistent with N credits and past PSNT surveys. When summarized by previous crop, soil nitrate values were similar for corn following cereals (predominantly wheat) or soybeans, but lower when following corn, again consistent with N credits (Table 2).

Table 1. Soil nitrate by soil texture

Soil Texture

Soil Nitrate (ppm)

Coarse

8.3

Fine

11.8

Medium

12.0

Table 2. Soil nitrate by previous crop

Previous Crop

Soil Nitrate (ppm)

Corn

6.7

Soybeans

11.4

Cereals

11.8

Recommendations:

In general, soil nitrate values are similar to average, suggesting normal nitrogen practices should be adequate for these sites this year. However, these values are a relative indication only, and should not be used as a recommendation for nitrogen rates on any given farm. Soil nitrate values are highly influenced by the environment (agronomic practices, local weather). For instance, if you are in an area which has received significantly more rainfall than other parts of the province, you may have also experienced more loss than is reflected in these results. The only way to know soil nitrate concentrations on your own farm is to pull soil nitrates from your own fields.

To collect PSNT samples, collect several 12″ soil samples across a field using a soil probe. Sample parts of fields differently if there is reason to suspect differences in N content (past history, soil type, topography etc.). Take a well-mixed representative sub sample of approximately 1 lb to fill a lab box or bag. Samples should be chilled to prevent further mineralization and sent to a lab as soon as possible. PSNT recommendations for a given soil nitrate test are only valid for natural soil nitrate supply, not valid where any nitrogen fertilizer would be collected in the sample (preplant, broadcast N). A modest amount of N applied with starter (ie. 30 lb/ac) is OK provided sampling can be taken mid-row to avoid these bands.

OMAFRA has recently revised PSNT recommendations to include both a soil nitrate measurement and an expected yield that can be achieved (Table 3).

Table 3. Revised PSNT Recommendations

Soil

Expected Yield (bu/ac)

Nitrate

120

143

167

191

215

239

(PPM)

Sidedress Nitrogen Fertilizer Recommendations (lb N/ac)

0

176

197

218

240

261

282

2.5

163

184

205

225

246

267

5

151

171

191

211

231

252

7.5

138

158

177

197

216

236

10

126

144

163

182

201

221

12.5

113

131

149

168

187

206

15

99

117

135

153

172

190

17.5

83

102

120

138

156

175

20

57

86

105

123

141

159

22.5

0

60

88

107

126

144

25

0

0

63

90

110

128

27.5

0

0

0

66

92

111

30

0

0

0

0

68

93

32.5

0

0

0

0

0

69

35

0

0

0

0

0

0

Thanks to our N-Sentinel trial co-operators, as well as Greg Stewart, Maizex Seeds for providing supplementary nitrate samples for the 2016 PSNT Survey.

The corn nitrogen calculator app generates a recommendation for the most economical N rate for a corn field. It is based on more than 40 years of Ontario research and takes into account soil type, rotation, and the cost scenario (i.e. anticipated cost of N and price of corn). The app allows you to save the recommendations for each field and to generate an email report.

“Carbon to nitrogen ratio imbalance” is a term used to describe a type of nitrogen deficiency. A field recently had pulp and paper biosolids applied. The newly planted crop looked great, until the seedlings ran out of seed reserves and started utilizing soil nutrients. The crop then turned a neon shade of yellow. What happened?

When an organic amendment is applied to a field, it adds nutrients and organic matter to the soil. . The carbon: nitrogen (C:N) ratio shows the proportion of organic carbon to total nitrogen of a manure or organic material.

The nitrogen is a food source for the micro-organisms (“soil bugs”) while they break down the carbon material. When the process is complete, the soil microbes die and decompose. The microbial nitrogen is then returned to the soil and becomes available to the plants. This is considered the “organic nitrogen” component of the organic materials. How long this process takes depends on the ratio of carbon to nitrogen in the material.

Liquid hog manure has a C:N ratio near 10:1. The nitrogen in liquid hog manure will become quickly available when the soil microbes are active in the soil. Pulp and papermill biosolids have a C: N ratio ranging from 25:1 to over 200:1, depending on how much nitrogen is added by the company producing the biosolids material. The nitrogen contribution from this material could take considerably more than one growing season to become available. To compensate for the high C: N ratio, some pulp and paper processors will add nitrogen to balance the carbon and reduce the ratio down to about 25:1. Each company provides a different product, so analysis of individual products is important.

Carbon to nitrogen ratio is not obvious by looking at the material. The C:N ratio of this compost material was analyzed at 12:1

The C: N ratio of soil is in the range of 8-10:1. When solid manure or other organic material has a C:N ratio of greater than 30:1, there is a higher risk that the soil micro-organisms will “steal” nitrogen from the soil and tie it up as they break down the carbon, which makes the nitrogen unavailable to a crop. A crop with higher nitrogen requirements, such as corn or wheat, will show nitrogen deficiencies in that situation. When a material has a C:N ratio less than 20:1, there is generally enough nitrogen in the organic material to break down the carbon without causing a nitrogen deficiency in the crop.

The OMAFRA field crop unit in collaboration with farm cooperators, agribusiness and SGS-AgriFood Labs conducted the annual survey of soil nitrate nitrogen levels across the province from June 3rd to June 5th, sampling over 130 fields. The samples were collected after heavy rainfall events during the weekend of May 30-31, where some areas received up to 10 cm (4″) although amounts varied widely. Rainfall events are known to reduce soil N levels due to leaching or denitrification. Delaying sampling a few days after significant rains is always advised but sometimes impossible based on corn stage etc.

The 2015 soil N survey targeted fields where N containing fertilizer was not broadcast applied this spring, had no recent history of manure and the previous year crop was corn, soybeans, edible beans or cereals. Medium textured soils (loam, silt loam and sandy clay loam) had soil nitrate levels that averaged 15.8 PPM (Table 1), which was 4-5 ppm higher than the surveys historic average of 11.0 PPM. Survey average nitrate levels for recent years on medium textured soils were 9.8 ppm in 2014 (wet May), 10.7 ppm in 2013 (cool wet spring), 12.2 PPM in 2012 (warm spring) and 9.5 PPM in 2011 (cool spring). Mineralization of organic nitrogen is influenced by temperature, precipitation, time and field history. Drier than normal spring conditions reduce the amount of N loss due to leaching or denitrification and probably explains the relatively high early June soil nitrate levels observed in the 2015 survey.

Spring nitrate levels in 2015 do not appear to be significantly affected by soil texture. Historically, soil nitrate levels have been lower on clay and sandy textured soils when compared to loam and silt loam soils. Sandy and clay soils are more sensitive to heavy rainfall in terms of nitrate loss (through leaching and denitrification respectively) and the dry spring conditions in 2015 minimized risk of N loss through these processes.

Previous crops (cereals vs. soybeans) usually had small effects on average soil nitrate levels observed in 2015 (Table 2). Where corn was the previous crop, sample numbers were small so an individual sample with high level can impact the average substantially.
On the medium and coarse soils nitrate levels averaged lower in no-till fields (Table 3). Tillage accelerates the rate of N release from organic matter and this process probably accounts for higher soil nitrate levels observed in mulch-till and conventional-till fields (Table 3).

Recommendations
The higher than usual average soil nitrate levels observed in this year’s survey suggests that fertilizer N requirements in 2015 may be less than the rates generally needed in most years. To confirm fertilizer N requirements for individual corn fields producers should be using a PSNT test on their fields to determine the adjustment amount of fertilizer nitrogen required compared to normal rates of nitrogen that they typically apply at side dress or with late applications (See Table 5). Where nitrogen has previously been applied and following some significant rain amounts, the high level of mineralization in 2015 suggests that sufficient nitrogen should be available to finish the crop.

A 1PPM change in PSNT test level suggests a change in recommendation of about 10 lbsN/ac. If the traditional average PPM level of soil nitrate for early June timing is 11.0 ppm, then normal rates of fertilizer nitrogen might be 40-50 lbsN/ac less this year because of higher than normal soil nitrate availability observed in many survey fields in 2015. This however, cannot be determined without taking a PSNT soil sample yourself.
Remember that soil nitrogen tests are based on a well-mixed composite of multiple 30cm/12inch cores collected across the field. Samples must be quickly cooled and kept cool in transport to the labs for rapid and accurate analysis.

A PSNT test taken in early June having a test value over 25ppm indicates that there is probably sufficient soil nitrogen supply to meet corn nitrogen requirements.

A PSNT test taken in early June having a test value over 25ppm indicates that there is probably sufficient soil nitrogen supply to meet corn nitrogen requirements. However, a change in the PSNT table to include “yield goal” as a parameter in the recommendation shows that the amount of nitrogen needed above 25ppm will occur under higher yield expectations (Table 4.)

The Nitrogen rates in Table 4 represent the total amount of Nitrogen recommended. Side dress rates applied should subtract the starter nitrogen rate already applied from the above table rates to determine the actual amount to apply as a side dress or in-crop broadcast application. The yield projections chosen must be “proven yields” that have occurred on the farm. Further research is needed to understand the amount of nitrogen made available to the crop from in-crop late spring applications of broadcast nitrogen (urea, dropped piped UAN, etc). The table values above are calibrated based on an injected side dress application method.

Where preplant nitrogen was previously broadcast to the field before soil sampling, this table does not offer reliable nitrogen recommendations.

Current P and K recommendations in Ontario guide crop producers to apply a rate of fertilizer that will provide the greatest potential of an economic response during the year of application. Increases in crop yields over time have resulted in higher nutrient removal rates which have decreased the “equilibrium” soil test values where average crop removal rates equal the recommended application rates. Recent research in Ontario has demonstrated that starter fertilizer can provide significant yield and economic gains on sites with low testing soils when sufficient rates of the proper product are applied (ie. high rates of dry fertilizer). Despite this, many question whether applying sufficient rates on low or medium testing soils can equal the yield potential attained for sites where fertility is built up to a non-responsive range and maintained. Building phosphorous and potassium levels in soil represents a significant expense to growers, and can pose economic (ie. land rental) and environmental (phosphorous runoff) risks. Due to the limited amount of data available, this research is being conducted to investigate how starter fertilizer selection (product, rate) and soil fertility management strategy (sufficiency or build and maintain) influence the economics and productivity of corn, soybeans and wheat over the long term in Ontario.

Project Objectives:

The key objectives of this project include:

Identify which fertilizer rates and application methods maximize net returns during the year of application

Identify over the longer term whether meeting fertilizer recommendations for a given fertilizer test will provide yield and net return stability equivalent to a build up an maintenance approach, particularly in a high yielding environment

Methods:

Two locations testing low to moderate in P and K (Table 1) were secured at Elora and Bornholm in 2012 while a third location at Lucan was secured for 2014. In addition a 4th site is being managed by Dr. David Hooker at Ridgetown Campus, U of Guelph. Each location has four main fertility blocks to investigate yield response between a “build and maintain” and “sufficiency” fertilizer approaches. Fertility blocks are currently being built up to non-responsive values through regular fall applications of broadcast fertilizer, and include a high soil test P, high soil test K, high soil test P and K, and a background P and K. Once high fertility blocks have been built, they will be maintained at those levels. Various starter fertilizers will be applied in a split-plot fashion across the main fertility blocks to investigate the interactions between starter fertilizer and soil fertility. Final broadcast by starter plots are 10’ wide and 60’ in length. Starter fertilizer treatments (Table 2) are applied to corn with a 4-row John Deere 7000 corn planter customized to deliver liquid or dry fertilizers either in-furrow or in 2”x2” bands.

Table 1. Soil test P and K of control plots at initiation of each trial

Location

Soil Test P

Soil Test K

ppm

Rating*

ppm

Rating*

Elora

11

MR

57

HR

Bornholm

20

MR

111

MR

Lucan

11

MR

118

MR

* where MR and HR denote moderate and high probabilities of response, respectively.

Corn, soybeans and wheat are present at each trial for each year, receive similar starter fertilizer treatments, and are rotated across crop blocks each year. All crops are harvested with a John Deere 6600 combine retrofitted with a batch-weigh hopper and moisture meter for individual plot weight and moisture measurements. Soil sampling of individual plots at Elora and Bornholm commenced in the fall of 2014 to evaluate soil fertility building to date. A timeline of trial establishment and data collection to date is presented in Table 2.

By the end of the 2014 growing season, the Elora and Bornholm trials have undergone three years of fertility building while the Lucan trial has only undergone one. Where no broadcast fertilizer was applied at Elora and Bornholm, starter fertilizers containing both P and K demonstrate clear yield responses, with a slight response to a low rate in-furrow liquid starter, and a large response to a high rate banded dry fertilizer (Figure 1). These responses are consistent with previous research at locations with low to moderate background fertility levels. Where P and K had been broadcast, this starter response is largely muted as all plots respond to the high rates of broadcast fertilizer. While a high rate P and K starter fertilizer provides a very large yield boost relative to no starter under the no-broadcast treatments, it did not appear to match the yield potential of where high rates of P and K had been broadcast, although these higher yields were attained in plots receiving over 4x as much product.

After one year of receiving a broadcast application, a slight yield response to starter fertilizer was observed across both the non-broadcast and broadcast P and K treatments at Lucan, for which the response was slightly higher for high rate banded fertilizer than the low rate in-furrow product. Yields under the no-broadcast treatments appeared to slightly lag yields under the broadcast P and K treatments. These relationships may change over time at Lucan as broadcast treatments are further built.

Given the fact that fertility building is still underway at these locations, conclusions and analysis of economic performance of the sufficiency and build-and-maintain approaches will not be applied until all locations receive multiple years of data under both a background and fully built fertility program.

Summary:

To date, three years of soil fertility building and yield data have been completed at Elora and Bornholm, while one year of soil building and yield data has been completed at Lucan. Soil testing has been conducted on a plot basis for the soil fertility building treatments at Elora and Bornholm. Looking at data averaged across both Elora and Bornholm, starter fertilizer responses are observed under non-broadcast treatments, but less so under broadcast. While the highest overall yields are always obtained under broadcast applications, these treatments have received over 4x the amount of fertility being applied through high rate starter. Final yield and economic performance will be evaluated once high fertility soil blocks have been built, and several years of data collected.

Next Steps:

Soil fertility building will continue as required at sites. Soil sampling will be conducted to monitor building or maintenance requirements. Crop planting with the various starter fertilizer treatments and yield monitoring will continue through to 2023.

Acknowledgements:

This project is funded by the Grain Farmers of Ontario (GFO) and the long term commitment to this type of project by the GFO is greatly appreciated. Appreciation is expressed to Middlesex SCIA for support on this project and for excellent technical support by Shane McClure and Ben Rosser.